This invention relates to fuel pumps and particularly to an automatic speed-control actuator for variable speed pumps.
Controls for the automatic regulation of fuel distribution pumps are not readily available on the market. Standard controls presently available would require extensive and expensive modifications involving considerable electronic circuitry to be capable of performing required functions provided by the instant invention.
The primary purpose of the control of this invention is to automatically regulate pump speed under varying inlet conditions to achieve a maximum pumping rate while not exceeding a selected pump discharge pressure or creating an excessive vacuum at the pump suction. This novel control is applicable to booster pumps operating with a positive pressure on both the inlet and outlet, and to lift pumps, where limiting the suction and discharge pressures is desired. The control of this invention will accomplish these results in a manner which is less costly and simpler to install and maintain than others presently available.
Old methods for pumping fuels, etc., over long distances usually necessitated shuttling fuel from one station to another requiring reservoirs, observers or operators to check on fuel supplies and communications from one pumping station to the next. However, with the present system, pumps can be connected in series and operate automatically, as described herein, without the need for reservoirs at each pump station, operators, etc.
U.S. Pat. No. 2,225,295 discloses an automatic control system for a suction dredge pump which actuates through the medium of a switch unit arranged in combination with a flow or velocity meter connected in communication with the discharge pipe of the pump. This control regulates the motor speed to maintain a constant flow velocity in the pump discharge and to stop the pump if there is no flow. The control of the present invention, however, regulates engine speed by monitoring the suction side of the pump as well as the discharge side and will regulate the engine speed to produce as near a vacuum as the inlet setting of the control will allow; in addition, the present invention will maintain a constant pressure on the discharge side of a pump even when there is no flow, and is designed for automatic operation of pumps in series as well as single pumps.
U.S. Pat. No. 2,651,995 relates to an automatic booster station for a pipe line pumping system which operates automatically and is responsive to changes in the rate flow of pipe line fluids; the system is provided with interlocking safety features to prevent damage in the event that any dangerous conditions are encountered. This device, however, utilizes a centrifugal switch attached to a flow meter to start and stop a pump; it does not adjust pump speed to compensate for changing flow conditions in the pipeline as is provided by the instant invention. The pressure switches used in this prior art patent are merely emergency safety switches.
U.S. Pat. No. 2,989,000 discloses a control designed to maintain a preset differential pressure across a pump. Whereas, the control of the present invention is to maintain a minimum suction pressure and/or a maximum discharge pressure, and any differential which occurs within these set limits is acceptable; if either suction or discharge pressure exceeds the set limits the present control device will slowly lower the engine speed looking for a point where the suction and discharge pressure conditions are acceptable, and if none is found the engine will run at a fixed idle until the pressure requirements are satisfied, at which time the pump will automatically resume normal operation. In the patented device, the control must be manually returned to normal operation following a low pressure shutdown.
In U.S. Pat. No. 3,072,058, a control system is disclosed for a pipe line pumping station having at least one pump driven by an electric motor by way of a variable mechanical coupling. The control used in this prior system monitors the power consumption of an electrically driven pump motor and regulates the pumping rate so as not to exceed an electrical power demand factor. The objective in this prior patent is to minimize power cost and is not related to changing speed to prevent unacceptable pressure changes as in the instant invention.